An array of conductive drive and sense electrodes may form a mutual-capacitance touch sensor having one or more capacitive nodes. The mutual-capacitance touch sensor may have either a two-layer configuration or single-layer configuration. In the two-layer configuration, drive electrodes may be disposed in a pattern on one side of a dielectric substrate and sense electrodes disposed in a pattern on another side of the substrate. An intersection of a drive electrode and a sense electrodes in the array may form a capacitive node. At the intersection, the drive and sense electrodes may come near each other, but they do not make electrical contact with each other. Instead, the sense electrode is capacitively coupled to the drive electrode. In the single-layer configuration, drive and sense electrodes may be disposed in a pattern on one side of a substrate. In such a configuration, a pair of drive and sense electrodes capacitively coupled to each other across a space or dielectric between electrodes may form a capacitive node.
A pulsed or, in some cases, alternating voltage applied to the drive electrode may induce a charge on the sense electrode, and the amount of charge induced may be susceptible to external influence (such as a touch by or the proximity of an object). When an object, separated from drive and sense electrodes by a dielectric layer, comes within proximity of the drive and sense electrodes, a change in capacitance may occur at that capacitive node and a controller may measure the change in capacitance as a change in voltage. By measuring voltages throughout the array and applying an algorithm to the measured signal, the controller may determine the position of the touch or proximity on the touch sensor.
In a single-layer configuration for a self-capacitance implementation, an array of vertical and horizontal conductive electrodes of only a single type (e.g. drive) may be disposed in a pattern on one side of the substrate. Each of the conductive electrodes in the array may form a capacitive node, and, when an object touches or comes within proximity of the electrode, a change in self-capacitance may occur at that capacitive node and a controller may measure the change in capacitance as a change in voltage or a change in the amount of charge needed to raise the voltage to some pre-determined amount. As with a mutual-capacitance touch screen, by measuring voltages throughout the array, the controller may determine the position of the touch or proximity on the touch sensor.
In a touch-sensitive display application, a touch screen may enable a user to interact directly with what is displayed on a display underneath the touch screen, rather than indirectly with a mouse or touchpad. A touch screen may be attached to or provided as part of, for example, a desktop computer, laptop computer, tablet computer, personal digital assistant (PDA), smartphone, satellite navigation device, portable media player, portable game console, kiosk computer, point-of-sale device, or other suitable device. A control panel on a household or other appliance may include a touch screen.